From 7ef4ae72a8578475064eb66e3ed5703ccf6ee078 Mon Sep 17 00:00:00 2001
From: Ruediger Pluem <r.pluem@gmx.de>
Date: Thu, 30 Apr 2020 07:56:01 +0200
Subject: [PATCH] Set SameSite to None on test cookie

If the SameSite cookie attribute is to be set because
MellonCookieSameSite is configured and MELLON_DISABLE_SAMESITE not set
for this particular request set it to None for the test cookie.
This ensures that the test cookie with the static test content does not
get lost in the HTTP-POST binding request issued by the autosubmit form
returned by the IDP.
Addresses #20

* auth_mellon.h: Add AM_FORCE_SAMESITE_NONE_NOTE

* auth_mellon_handler.c (am_send_login_authn_request): Set request note
  to set SameSite to None if appropriate.

* auth_mellon_cookie.c (am_cookie_params): Set SameSite to None if
  requested via request note.
---
 auth_mellon.h         | 3 +++
 auth_mellon_cookie.c  | 6 +++++-
 auth_mellon_handler.c | 5 +++++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/auth_mellon.h b/auth_mellon.h
index fd39b28..401ed9c 100644
--- a/auth_mellon.h
+++ b/auth_mellon.h
@@ -100,6 +100,9 @@ typedef enum {
 /* Disable SameSite Environment Value */
 #define AM_DISABLE_SAMESITE_ENV_VAR "MELLON_DISABLE_SAMESITE"
 
+/* Force setting SameSite to None */
+#define AM_FORCE_SAMESITE_NONE_NOTE "MELLON_FORCE_SAMESITE_NONE"
+
 
 /* This is the length of the id we use (for session IDs and
  * replaying POST data).
diff --git a/auth_mellon_cookie.c b/auth_mellon_cookie.c
index 55f77a5..6bff81e 100644
--- a/auth_mellon_cookie.c
+++ b/auth_mellon_cookie.c
@@ -78,7 +78,11 @@ static const char *am_cookie_params(request_rec *r)
     }
 
     if (env_var_value == NULL){
-        if (cfg->cookie_samesite == am_samesite_lax) {
+        if ((cfg->cookie_samesite != am_samesite_default) &&
+            (apr_table_get(r->notes, AM_FORCE_SAMESITE_NONE_NOTE) != NULL)) {
+            cookie_samesite = "; SameSite=None";
+        }
+        else if (cfg->cookie_samesite == am_samesite_lax) {
             cookie_samesite = "; SameSite=Lax";
         } else if (cfg->cookie_samesite == am_samesite_strict) {
             cookie_samesite = "; SameSite=Strict";
diff --git a/auth_mellon_handler.c b/auth_mellon_handler.c
index 395ee1d..40c9bcd 100644
--- a/auth_mellon_handler.c
+++ b/auth_mellon_handler.c
@@ -3261,8 +3261,13 @@ static int am_send_login_authn_request(request_rec *r, const char *idp,
     /* Add cookie for cookie test. We know that we should have
      * a valid cookie when we return from the IdP after SP-initiated
      * login.
+     * Ensure that SameSite is set to None for this cookie if SameSite
+     * is allowed to be set as the cookie otherwise gets lost on
+     * HTTP-POST binding messages.
      */
+    apr_table_setn(r->notes, AM_FORCE_SAMESITE_NONE_NOTE, "1");
     am_cookie_set(r, "cookietest");
+    apr_table_unset(r->notes, AM_FORCE_SAMESITE_NONE_NOTE);
 
     server = am_get_lasso_server(r);
     if(server == NULL) {
-- 
2.26.2